U.S. patent application number 14/416096 was filed with the patent office on 2015-08-13 for lighting device, display device and television device.
The applicant listed for this patent is Sharp Kabushiki Kaisha. Invention is credited to Takaharu Shimizu.
Application Number | 20150226913 14/416096 |
Document ID | / |
Family ID | 50027978 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150226913 |
Kind Code |
A1 |
Shimizu; Takaharu |
August 13, 2015 |
LIGHTING DEVICE, DISPLAY DEVICE AND TELEVISION DEVICE
Abstract
A backlight unit 24 includes LEDs 28, a light guide plate 20, a
heat dissipation member 36, LED boards 30, and adhesive tapes 38.
The light guide plate 20 includes a front surface configured as a
light exit surface 20b, a rear plate surface as an opposite surface
20c that is opposite from the light exit surface 20b, long
side-surfaces configured as light entrance surfaces 20a. The light
guide plate 20 is arranged such that the light entrance surface 20a
faces the LEDs 28 and configured to guide light from the LEDs 28.
The heat dissipation member 36 includes at least a plate-like
portion 36a arranged adjacent to the opposite surface 20c and has
heat dissipation properties. Each LED board 30 includes an opposed
surface 30a1 that is opposed to the opposite surface 20c and
arranged on the plate-like portion so as to be slidable with
respect to a direction perpendicular to the light entrance surface
20a. The LEDs 28 are mounted on a mounting portion 30b of the heat
dissipation member 36. The adhesive tapes 38 are arranged between
the opposite surface 20c and the opposed surface 30a1. The LED
boards 30 are attached to the light guide plate with the adhesive
tapes 38.
Inventors: |
Shimizu; Takaharu;
(Osaka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sharp Kabushiki Kaisha |
Osaka-shi, Osaka |
|
JP |
|
|
Family ID: |
50027978 |
Appl. No.: |
14/416096 |
Filed: |
July 30, 2013 |
PCT Filed: |
July 30, 2013 |
PCT NO: |
PCT/JP2013/070578 |
371 Date: |
January 21, 2015 |
Current U.S.
Class: |
348/836 ; 349/65;
362/609; 362/611 |
Current CPC
Class: |
G02B 6/0086 20130101;
G02B 6/0065 20130101; G02B 6/0073 20130101; G02B 6/0091 20130101;
G02B 6/0031 20130101; G02B 6/0068 20130101; G02B 6/0085 20130101;
H04N 5/64 20130101 |
International
Class: |
F21V 8/00 20060101
F21V008/00; H04N 5/64 20060101 H04N005/64 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2012 |
JP |
2012-172785 |
Claims
1. A lighting device comprising: a light source; a light guide
plate including a plate surface configured as a light exit surface,
another plate surface as an opposite surface being opposite from
the light exit surface, and at least one side surface configured as
a light entrance surface, the light guide plate being arranged such
that the light entrance surface is opposite the light source and
configured to guide light from the light source; a heat dissipation
member having a heat dissipation property and including at least
one plate-like portion arranged adjacent to the opposite surface
and; a light source board having the light source mounted on a part
thereof and including an opposed surface that is opposed to the
opposite surface, the light source board being arranged on the
plate-like portion so as to be slidable in a direction
perpendicular to the light entrance surface; and an adhesive tape
arranged between the opposite surface and the opposed surface and
with which the light source board is attached to the light guide
plate.
2. The lighting device according to claim 1, wherein the adhesive
tape includes a pair of adhesive tapes between the opposite surface
and the opposed surface, the lighting device further comprising a
reflection member arranged between the pair of the adhesive tapes,
and the reflection member includes an edge portion that extends
closer to the light source than the light entrance surface of the
light guide plate is.
3. The lighting device according to claim 2, wherein the light
source board includes a mounting portion where the light source is
mounted, the mounting portion having a plate-like shape and
extending from the opposed surface toward a light exit surface
side.
4. The lighting device according to claim 1, wherein the light
source is mounted on the opposed surface in a standing position,
the light source including a light emitting surface on a side
surface thereof.
5. The lighting device according to claim 1, further comprising a
chassis holding at least the light source, the light guide plate,
and the light source board, wherein the heat dissipation member is
configured as a portion of the chassis.
6. The lighting device according to claim 1, wherein the light
source board is made of aluminum.
7. The lighting device according to claim 1, the light guide plate
includes a plurality of side surfaces each configured as the light
entrance surface.
8. A display device comprising: a display panel displaying an image
using light from the lighting device according to claim 1.
9. The display device according to claim 8, wherein the display
panel is a liquid crystal panel including liquid crystals.
10. A television device comprising the display device according to
claim 8.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lighting device, a
display device, and a television device.
BACKGROUND ART
[0002] Displays in image display devices, such as television
devices, are now being shifted from conventional cathode-ray tube
displays to thin displays, such as liquid crystal displays and
plasma displays. With the thin displays, the thicknesses of the
image display devices can be reduced. Liquid crystal panels
included in the liquid crystal display devices do not emit light,
and thus backlight devices are required as separate lighting
devices. An edge light-type backlight device including a light
guide plate with a light entrance surface on the side and light
sources such as LEDs arranged closer to the side of the light guide
plate is known as an example of such backlight devices.
[0003] In the edge-light type backlight unit, it is required to
improve light entering efficiency by reducing a distance between
the light sources and the light entrance surface of the light guide
plate. If the light sources are too close to the light entrance
surface, the light entrance surface may come in contact with the
light sources when thermal expansion of the light guide plate
occurs. This may damage the light sources. Therefore, a
predetermined distance is required between the light sources and
the light entrance surface of the light guide plate.
[0004] Patent document 1 discloses an edge-light type lighting
device in which light entrance efficiency is improved. In the
lighting device, the position of a light guide plate is fixed by
locking the light guide plate with respect to a direction
perpendicular to the light entrance surface. According to this
configuration, a shift in position of the light guide plate is less
likely to occur even if thermal expansion of the light guide plate
occurs. In other words, even if the light guide plate thermally
expands, the light entrance surface is less likely to come in
contact with the light sources. Therefore, the lighting device has
a configuration in which the distance between the light sources and
the light entrance surface of the light guide plate is reduced and
thus the light entering efficiency of light emitted from the light
source is improved.
RELATED ART DOCUMENT
Patent Document
[0005] Patent Document 1: Japanese Unexamined Patent Application
Publication No. 2011-150264
Problem to be Solved by the Invention
[0006] The backlight device of the Patent document 1 does not
include a proper configuration for releasing heat generated around
the light sources. While the light sources are on, heat may stay
inside the housing. If heat stays inside the housing, a temperature
within the housing increases and this may be factors to cause
several defects.
DISCLOSURE OF THE PRESENT INVENTION
[0007] The technology described in this specification was made in
view of the foregoing circumstances. An object is to provide a
lighting device having heat dissipation properties and in which
light entering efficiency of light emitted from a light source into
a light entrance surface of a light guide plate is improved.
Means for Solving the Problem
[0008] Technologies described herein are related to a lighting
device having the following configurations. The lighting device
includes alight source, alight guide plate, alight source board, a
heat dissipation member, and an adhesive tape. The light guide
plate includes a plate surface configured as a light exit surface,
another plate surface as an opposite surface that is opposite from
the light exit surface, and at least one side surface configured as
a light entrance surface. The light guide plate is arranged such
that the light entrance surface is opposite the light source and
configured to guide light from the light source. The heat
dissipation member having a heat dissipation property includes at
least one plate-like portion arranged adjacent to the opposite
surface. The light source board includes an opposed surface that is
opposite the opposite surface. The light source board is arranged
on the plate-like portion so as to be slidable in a direction
perpendicular to the light entrance surface. The light source is
mounted to a portion of the light source board. The adhesive tape
is arranged between the opposite surface and the opposed surface.
The light source board is attached to the light guide plate with
the adhesive tape.
[0009] According to the lighting device, the light source board is
attached to the light guide plate with the adhesive tape and thus
the light source board is fixed to the light guide plate. According
to this configuration, a distance between the light source and the
light entrance surface is maintained. The light source board is
arranged so as to be slidable on the plate-like portion. If the
light entrance surface of the light guide plate thermally expands
toward the light source, the light source board that is fixed to
the light guide plate moves according to the thermal expansion of
the light guide plate. Therefore, a distance between the light
source and the light entrance surface remains constant before and
after the thermal expansion. In this configuration, a predetermined
distance is not required between the light source and the light
entrance surface for a supposed thermal expansion of the light
guide plate. Therefore, the light source can be arranged close to
the light entrance surface and thus light entering efficiency of
light from the light source into the light entrance surface is
improved. Furthermore, the light source board is arranged on the
heat dissipation member having a heat dissipation property.
Therefore, heat generated around the light source is effectively
dissipated via the heat dissipation member. According to this
configuration, while the lighting device has the heat dissipation
property, the light entering efficiency of the light emitted from
the light source into the light entrance surface is improved.
[0010] A pair of the adhesive tapes may be arranged between the
opposite surface and the opposed surface. The lighting device may
further include a reflection member arranged between the pair of
the adhesive tapes. The reflection member may include an edge
portion that extends closer to the light source than the light
entrance surface of the light guide plate is.
[0011] According to this configuration, light that exits the light
source and travels to the opposed surface is reflected by the
extending portion of the reflection member and directed toward the
light entrance surface. Therefore, the light entering efficiency of
light emitted from the light source into the light entrance surface
is further improved.
[0012] The light source board may include a mounting portion where
the light source is mounted. The mounting portion may have a
plate-like shape and extend from the opposed surface toward a light
exit surface side.
[0013] In this configuration, the edge portion of the reflection
member can be extended to a position between the light source and
the opposed surface (i.e., immediately below the light source).
Therefore, light from the light source is effectively reflected
toward the light entrance surface by the reflection member.
[0014] The light source may be mounted on the opposed surface in a
standing position. The light source includes a light emitting
surface on a side surface thereof.
[0015] According to this configuration, the light source board does
not need a portion that extends from the opposed surface and to
which the light source are attached. In this configuration, a
bending work is not required for the light source board and thus
the production cost can be reduced.
[0016] The lighting device may further include a chassis that holds
at least the light source, the light guide plate, and the light
source board. The heat dissipation member may be configured as a
portion of the chassis.
[0017] According to this configuration, the heat dissipation member
and the chassis are connected together to form a single component.
Therefore, reduction in thickness of the lighting device is
accomplished.
[0018] The light source board may be made of aluminum.
[0019] According to this configuration, the light source board is a
member having high thermal conductivity. Therefore, heat generated
from the light source is effectively transferred to the heat
dissipation member via the light source board.
[0020] The light guide plate may include a plurality of side
surfaces each configured as the light entrance surface.
[0021] According to this configuration, the light sources are
arranged corresponding to multiple light entrance surfaces. The
light sources are arranged close to each of the light entrance
surfaces and thus light entering efficiency of light into each of
the light entrance surfaces is improved. Therefore, brightness of
the lighting device is improved.
[0022] The technologies described in this specification may be
applied to a display device including a display panel configured to
provide display using light from the above-described lighting
device. A display device that includes a liquid crystal panel as
such a display panel may be considered as new and advantageous.
Furthermore, a television device including the above-described
display device may be considered as new and advantageous. In the
above-described display device or the above-described television
device, a display area can be increased.
Advantageous Effect of the Invention
[0023] According to the technologies described in this
specification, a lighting device having heat dissipation properties
and improved light entering efficiency of light emitted from a
light source into light entrance surface of a light guide plate is
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is an exploded perspective view illustrating a
general configuration of a television device TV according to a
first embodiment of the invention.
[0025] FIG. 2 is an exploded perspective view of a liquid crystal
display device 10 illustrating a general configuration of the
liquid crystal display device 10.
[0026] FIG. 3 is a cross-sectional view of the liquid crystal
display device 10 along a short-side direction thereof illustrating
a cross-sectional configuration.
[0027] FIG. 4 is a magnified cross-sectional view of a relevant
portion of the liquid crystal display device 10 in FIG. 3
illustrating adhesive tapes 38 and therearound.
[0028] FIG. 5 is a magnified perspective front view of a light
guide plate 20, illustrating a light entrance surface 20a and its
vicinity.
[0029] FIG. 6 is a cross-sectional view of a liquid crystal display
device 110 according to a second embodiment taken along a
short-side direction thereof, illustrating a cross-sectional
configuration.
[0030] FIG. 7 is a magnified cross-sectional view of a relevant
portion of the liquid crystal display device 10 in FIG. 6,
illustrating adhesive tapes 138 and its vicinity.
[0031] FIG. 8 is a magnified cross-sectional view of a relevant
portion of a liquid crystal display device 210 according to a third
embodiment, illustrating adhesive tapes 238 and its vicinity.
[0032] FIG. 9 is a magnified cross-sectional view of a relevant
portion of a liquid crystal display device 310 according to a
fourth embodiment, illustrating adhesive tapes 338 and its
vicinity
[0033] FIG. 10 is an exploded perspective view illustrating a
general configuration of a liquid crystal display device 410
according to a fifth embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0034] A first embodiment will be described with reference to the
drawings. In the following description, a liquid crystal display
device 10 will be described. X-axes, Y-axes and Z-axes are provided
in portions of the drawings, respectively. The axes in each drawing
correspond to the respective axes in other drawings. The X-axes and
Y-axes are aligned with the horizontal direction and the vertical
direction, respectively. In the following description, the
top-bottom direction corresponds to the vertical direction unless
otherwise specified.
[0035] A television device TV includes the liquid crystal display
device (an example of a display device) 10, front and rear cabinets
Ca, Cb that hold the liquid crystal display device 10 therebetween,
a power source P, a tuner T, and a stand S. In FIG. 2, the upper
side and the lower side correspond to the front side and the rear
side of the liquid crystal display device 10, respectively. As
illustrated in FIG. 2, an overall shape of the liquid crystal
display device 10 is a landscape rectangular. The liquid crystal
display device 10 includes a liquid crystal panel 16 and a
backlight unit (an example of a lighting device) 24. The liquid
crystal panel 16 is a display panel and the backlight unit 24 is an
external light source. The liquid crystal panel 16 and the
backlight unit 24 are integrally held with a bezel 12 having a
frame-like shape.
[0036] As illustrated in FIG. 2, components of the liquid crystal
display device 10 are arranged in a space provided between the
bezel 12 that provides a front external configuration and a chassis
22 that provides a rear external configuration. The components
arranged between the bezel 12 and the chassis 22 are at least the
liquid crystal panel 16, a frame 14, an optical member 18, a light
guide plate 20, and LED units LU. The frame 14 having a frame-like
shape is arranged along edge areas of a front surface of the light
guide plate 20 (a light exit surface 20b). The frame 14 supports
the liquid crystal panel 16 with inner edge portions of the frame
14. The liquid crystal panel 16 and the optical member 18 are apart
from each other with the inner edge portions of the frame 14
therebetween. The optical member 18 is placed on the light guide
plate 20. The backlight unit 24 includes the optical member 18, the
light guide plate 20, the LED units LU, and the chassis 22. Namely,
the liquid crystal display device 10 without the bezel 12, the
liquid crystal panel 16 and the frame 14 is the backlight unit 24.
The backlight unit 24 includes LED boards 30 that are arranged in
the chassis 22 so as to face respective long-side edge surfaces of
the light guide plate 20. Each component will be described
next.
[0037] The liquid crystal panel 16 includes a pair of transparent
glass substrates (having a high light transmission capability) and
a liquid crystal layer (not illustrated). The glass substrates are
bonded together with a predetermined gap therebetween. The liquid
crystal layer is sealed between the glass substrates. On one of the
glass substrates, switching components (e.g., TFTs) connected to
source lines and gate lines that are perpendicular to each other,
pixel electrodes connected to the switching components, and an
alignment film are provided. On the other substrate, a color filter
having color sections such as R (red), G (green) and B (blue) color
sections arranged in a predetermined pattern, counter electrodes
and an alignment film are provided. Image data and various control
signals are transmitted from a driver circuit board (not
illustrated) to the source lines, the gate lines, and the counter
electrodes for displaying images. Polarizing plates (not
illustrated) are attached to outer surfaces of the glass
substrates.
[0038] As illustrated in FIG. 2, similar to the liquid crystal
panel 16, the optical member 18 has a landscape rectangular shape
in a plan view and has the same size (i.e., a short-side dimension
and a long-side dimension) as the liquid crystal panel 16. The
optical member 18 is placed on a front surface of the light guide
plate 20 (i.e., the light exit surface 20b). The optical member 18
includes three sheets that are placed on top of one another.
Specifically, a diffuser sheet 18a, a lens sheet (a prism sheet)
18b, and a reflecting type polarizing sheet 18c are placed on top
of one another in this sequence from the rear side (the light guide
plate 16 side). Each of the three sheets 18a, 18b, and 18c has the
substantially same size in a plan view.
[0039] The light guide plate 20 is made of substantially
transparent (high light transmissivity) synthetic resin (e.g.
acrylic resin or polycarbonate such as PMMA) which has a refractive
index sufficiently higher than that of the air. As illustrated in
FIG. 2, the light guide plate 20 has a landscape rectangular shape
in a plan view similar to the liquid crystal panel 16 and the
optical member 18. A thickness of the light guide plate 20 is
larger than a thickness of the optical member 18. A long-side
direction and a short-side direction of a main surface of the light
guide plate 20 correspond to the X-axis direction and the Y-axis
direction, respectively. A thickness direction of the light guide
plate 20 that is perpendicular to the main surface of the light
guide plate 20 corresponds to the Z-axis direction. The light guide
plate 20 is arranged on the rear side of the optical member 18 and
spaced away from a bottom plate 22a of the chassis 22. As
illustrated in FIG. 3, at least a short-side dimension of the light
guide plate 20 is the same as short-side dimensions of the liquid
crystal panel 16 and the optical member 18. The LED units LU are
arranged on sides of the short dimension of the light guide plate
16 so as to have the light guide plate 20 between the LED units LU
in the Y-axis direction. Rays of light from the LEDs 28 enter the
light guide plate 20 through the respective ends of the short-side
dimension of the light guide plate 20. The light guide plate 20 is
configured to guide the rays of light, which are from the LEDs 28
and enter the light guide plate 20 through the ends of the short
dimension thereof, toward the optical member 18 (on the front
side). In the backlight unit 24 according to this embodiment, the
light guide plate 20 and the optical member 18 are arranged behind
the liquid crystal panel 16 and the LED units LU, which are light
sources, are arranged at the side edges of the light guide plate
20. Namely, an edge lighting method (a side lighting method) is
adapted to the backlight unit 24.
[0040] One of main surfaces of the light guide plate 20 facing the
front side (a surface opposite the optical member 18) is the light
exit surface 20b. Light exits the light guide plate 20 through the
light exit surface 20b toward the optical member 18 and the liquid
crystal panel 16. The light guide plate 20 includes edge surfaces
that are adjacent to the main surfaces of the light guide plate 20.
Two of the edge surfaces on the long sides (i.e., end surfaces of
the short dimension) which have elongated shapes along the X-axis
direction are opposite the LEDs 28. The edge surfaces on the long
sides are the light entrance surfaces 20a. As illustrated in FIG.
4, a reflection sheet 20 is arranged on the rear side of the light
guide plate 20, which is, on an opposite surface 20c that is
opposite from the light exit surface 20b (a surface opposite the
chassis 22). The reflection sheet 26 is arranged to cover
substantially an entire area of the opposite surface 20c. On
long-side edge portions of the opposite surface 20c, adhesive tapes
38, which will be described later, are attached.
[0041] The reflection sheet 20 is in contact with the opposite
surface 20c of the light guide plate 20 but apart from bottom plate
portions 36a of heat dissipation members 36 and the bottom plate
22a of the chassis 22. The reflection sheet 26 is made of synthetic
resin and has a white surface that has high light reflectivity. In
this configuration, light that exits the light guide plate 20
through the opposite surface 20c toward the rear side is reflected
by the reflection sheet 26 toward the front side. The reflection
sheet 26 has a short-side dimension smaller than a short-side
dimension of the light guide plate 20.
[0042] As illustrated in FIG. 2, an overall shape of the chassis 22
is landscape rectangular and box-like to cover a substantially
overall areas of the light guide plate 20 and the LED units LU from
the rear side. The chassis 22 is made of metal, for instance,
aluminum-based material. The chassis 22 includes the bottom plate
22a, sidewalls 22b, 22b that upstand from the respective long edges
of the bottom plate 22a, and sidewalls that upstand from the
respective short edges of the bottom plate 22a. In the chassis 22,
space between the LED units LU, LU is a holding space for the light
guide plate 20. A power supply circuit board for supplying power to
the LED units LU is mounted to the back surface of the bottom plate
22a (not illustrated).
[0043] Next, configurations of the LEDs 28, the LED boards 30, and
heat dissipation members 36 included in the LED units LU will be
described. Each of the LEDs 28 of the LED units LU includes an LED
chip (not illustrated). The LED chips are mounted on boards that
are attached on a surface of a mounting portion 30b of the LED
board 30, which will be described later, opposite the light guide
plate 20. The LED chips are sealed with resin. The LED chip mounted
on the board has one main light emission wavelength. Specifically,
the LED chip that emits light in a single color of blue is used.
The resin that seals the LED chip contains phosphors dispersed
therein. The phosphors emit light in a predetermined color when
excited by blue light emitted from the LED chip. Thus, overall
color of light emitted from the LED 28 is white. The phosphors may
be selected, as appropriate, from yellow phosphors that emit yellow
light, green phosphors that emit green light, and red phosphors
that emit red light. The phosphors may be used in combination of
the above phosphors or one single one of the phosphors may be used.
Each LED 28 has a rectangular shape in a front view. The LED 28
includes a main light-emitting surface 28a that is opposite the
light entrance surface 20a of the light guide plate 20. Namely, the
LED 28 is a so-called top-surface-emitting type LED having a light
distribution according to the Lambertian distribution. The LED 28
has a long dimension in the Z-axis direction substantially the same
as a thickness of the light guide plate 20. The LED 28 includes a
front side-surface and a rear side-surface. The position of the
front side-surface with respect to the Z-axis direction is aligned
with the position of the light exit surface 20b of the light guide
plate 20 (refer to FIG. 4). The position of the rear side-surface
with respect to the Z-axis direction is aligned with the position
of the opposite surface 20c of the light guide plate 20. As
illustrated in FIG. 4, the main light-emitting surfaces 28a of the
LEDs 28 are located close to the light entrance surface 20a of the
light guide plate 20. With this configuration, high light entering
efficiency of light from the LEDs 28 into the light entrance
surface 20a is achieved.
[0044] The LED boards 30 of the LED units LU are made of aluminum
and have high heat dissipation properties. As illustrated in FIGS.
4 and 5, the LED board 30 includes a heat dissipating portion 30a
and the mounting portion 30b that form an angle therebetween so as
to have an L-like shape in a cross-section. The heat dissipating
portion 30a is in surface-contact with a plate-like portion 36a of
the heat dissipation member 36, which will be described later. The
mounting portion 30b is a portion to which the LEDs 28 are
attached. The LED board 30 has a long-side dimension substantially
the same as the long-side dimension of the light guide plate 20. As
illustrated in FIGS. 4 and 5, the mounting portion 30b has a
plate-like shape parallel to the light entrance surface 16b of the
light guide plate 16. A long-side direction, a short-side
direction, and a thickness direction of the mounting portion 30b
correspond to the X-axis direction, the Z-axis direction, and the
Y-axis direction, respectively. The LEDs 28 are mounted on an inner
plate surface of the mounting portion 30b, that is, a plate surface
that faces the light guide plate 20. While the mounting portion 30b
has the long-side dimension that is substantially the same as the
long-side dimension of the light guide plate 20, a short-side
dimension of the mounting portion 30b is larger than the thickness
of the light guide plate 20. An edge portion of the short dimension
of the mounting portion 30b (i.e., an edge on the rear side)
extends outward in the Z-axis direction over the opposite surface
20c of the light guide plate 20. An outer plate surface of the
mounting portion 30b, that is, a plate surface of the mounting
portion 30b opposite from the plate surface on which the LEDs 28
are mounted, faces a stand-up portion 36b of the heat dissipation
member 36, which will be described later.
[0045] As illustrated in FIGS. 4 and 5, the heat dissipating
portion 30a of the LED board 30 has a plate-like shape that is
parallel to the opposite surface 20c of the light guide plate 20. A
long-side direction, a short-side direction, and a thickness
direction of the heat dissipating portion 30a correspond to the
X-axis direction, the Y-axis direction, and the Z-axis direction,
respectively. The heat dissipating portion 30a extends inward from
the rear edge of the mounting portion 30b (an edge of the mounting
portion 30b on the chassis 22 side) in the Y-axis direction. In
other words, the heat dissipating portion 30a extends toward an
inner portion of the light guide plate 20. The heat dissipating
portion 30a has a long-side dimension substantially the same as the
long-side dimension of the mounting portion 30b. A front surface of
the heat dissipating portion 30a is an opposed surface 30a1 that
faces the opposite surface 20c of the light guide plate 20. A
portion of the opposed surface 30a1 is located behind the
reflection sheet 26. On another portion of the opposed surface
30a1, the adhesive tape 38, which will be described later, is
attached. The opposed surface 30a1 and the opposite surface 20c of
the light guide plate 20 are attached to the adhesive tapes 38, and
thus the heat dissipating portion 30a is fixed to the opposite
surface 20c. An overall area of a rear plate surface of the heat
dissipating portion 30a, that is, a plate surface of the heat
dissipating portion 30a that faces the heat dissipation member 36,
is in surface-contact with a plate surface of the heat dissipation
member 36 (specifically, a plate surface of the plate-like portion
36a). Although the heat dissipating portion 30a is in
surface-contact with the plate-like portion 36a of the heat
dissipation member 36, the heat dissipating portion 30a is not
fixed to the heat dissipation member 36. Therefore, the heat
dissipating portion 30a is slidable on the plate-like portion 36a
of the heat dissipation member 36 with respect to a direction
perpendicular to the light entrance surface 20a (i.e. the Y-axis
direction). With the heat dissipating portions 30a that are
entirely in surface-contact with the plate surface of the chassis
22, heat generated from the LEDs 28 that are turned on is
effectively transferred to the heat dissipation member 36 via the
mounting portion 30b and the heat dissipating portion 30a.
[0046] The heat dissipation member 36 of the LED unit LU is made of
metal having high thermal conductivity, such as aluminum. As
illustrated in FIGS. 4 and 5, the heat dissipation member 36 has a
size slightly larger than the LED board 30. The heat dissipation
member 36 includes the plate-like portion 36a and the stand-up
portion 36b. Similar to the LED boards 30, the plate-like portion
36a and the stand-up portion 36b form an angle therebetween so as
to have an L-like shape in a cross-section. As illustrated in FIGS.
4 and 5, the stand-up portion 36b extends from an outer edge of the
plate-like portion 36a, which will be described later, in the
Z-axis direction toward the front side, that is, toward the frame
14. The stand-up portion 36b has a plate-like shape that is
parallel to the light entrance surface 20a of the light guide plate
20. A long-side direction, a short-side direction, and a thickness
direction of the stand-up portion 36b are aligned with the X-axis
direction, the Z-axis direction, and the Y-axis direction,
respectively. The stand-up portion 36b includes an inner surface,
that is, a plate surface that faces the light guide plate 20. The
inner surface of the stand-up portion 36b is opposite a surface of
the mounting portion 30b of the LED board 30 opposite from the
surface on which the LEDs 28 are mounted. The stand-up portion 36b
has a long-side dimension that is substantially equal to the
long-side dimension of the mounting portion 30b of the LED board
30. A short-side dimension of the stand-up portion 36b is larger
than a short-side dimension of the mounting portion 30b of the LED
board 30. Therefore, an edge of the short dimension of the stand-up
portion 36b (an edge on the rear side) protrudes in the Z-axis
direction over the mounting portion 30b. Entire outer plate
surfaces of the stand-up portions 36b, which are plate surfaces
opposite from the surfaces that face the mounting portions 30b, are
in surface-contact with inner surfaces of the corresponding
long-side sidewalls 22b of the chassis 22.
[0047] As illustrated in FIGS. 4 and 5, the plate-like portion 36a
has a plate-like shape and is parallel to the bottom plate 22a of
the chassis 22. A long-side direction, a short-side direction, and
a thickness direction of the plate-like portion 36a are aligned
with the X-axis direction, the Y-axis direction, and the Z-axis
direction, respectively. The plate-like portion 36a extends inward
from the rear edge of the stand-up portion 36b (an edge of the
stand-up portion 36b on the chassis 22 side) in the Y-axis
direction. In other words, the plate-like portion 36a extends
toward an inner portion of the light guide plate 20. A large
portion of the plate-like portion 36a is in surface-contact with a
rear surface of the heat dissipating portion 30a. In other words, a
large portion of the plate-like portion 36a is sandwiched (located)
between the LED board 30 and the chassis 22. An entire rear plate
surface of the plate-like portion 36a, i.e., a plate surface of the
plate-like portion 36a that faces the chassis 22, is in
surface-contact with the plate surface of the bottom plate 22a of
the chassis 22. With the plate-like portions 36a of the heat
dissipation members 36 that are screwed to the bottom plate 22a of
the chassis 22, the heat dissipation members 36 are fixed to the
chassis 22.
[0048] Next, configurations and functions of the adhesive tapes 38
and reflection members 40, which are relevant components in this
embodiment, will be described. As illustrated in FIGS. 4 and 5, the
reflection member 40 and a pair of adhesive tapes 38, 38 that
sandwiches the reflection member 40 therebetween are arranged in a
space between the opposite surface 20c of the light guide plate 20
and the opposed surface 30a1 of the LED board 30. Each adhesive
tape 38 has adhesive surfaces on a front side and a rear side. One
of the adhesive tapes 38 and 38 is attached to the opposite surface
20c of the light guide plate 20 and the other one of the adhesive
tapes 38 is attached to the opposed surface 30a1. Specifically, the
one adhesive tape 38 is attached to a portion of the opposite
surface 20c close to the light entrance surface 20a (i.e., a
portion where the reflection sheet 26 is not arranged). The other
adhesive tape 38 is attached to a portion of the opposed surface
30a1 where the one adhesive tape 38 overlaps in a plan view. The
reflection member 40 having a sheet-like shape is arranged so as to
be sandwiched between the adhesive tapes 38, 38 and attached to the
respective adhesive tapes 38, 38. The adhesive tapes 38, 38 having
a length equal to a long dimension of the light guide plate 20 are
attached to the opposite surface 20c and the opposed surface 30a1,
respectively. With this configuration, the heat dissipating portion
30a of the LED board 30 is fixed to the portion of the opposite
surface 20c of the light guide plate 20 close to the light entrance
surface 20a. The adhesive tapes 38, 38 are attached to the opposite
surface 20c and the opposed surface 30a1, respectively, such that
edges of the respective adhesive tapes 38, 38 are aligned with the
light entrance surface 20a of the light guide plate 20.
[0049] The reflection members 40 are sheet-like members having
light reflection properties, similar to the reflection sheet 26. As
illustrated in FIG. 5, the reflection member 40 has a length (a
dimension in the X-axis direction) substantially the same as the
length of the adhesive tape 38. One edge of the reflection member
40 extends toward the LEDs 28 over the light entrance surface 20a
of the light guide plate 20 (the extending portion is hereinafter
referred to as an extending portion 40a). As illustrated in FIG. 5,
the extending portion 40a extends to a position immediately below
the LEDs 28. Namely, the reflection member 40 is arranged such that
a surface thereof faces a space between the main light-emitting
surfaces 28a of the LEDs 28 and the light entrance surface 20a of
the light guide plate 20. In this configuration, a large amount of
light that exits the LEDs 28 and travels toward a lower side (a
heat dissipating portion 30a side) is reflected by the reflection
member 40 toward the light entrance surface 20a. Therefore, light
entering efficiency of light that exits the LEDs 28 and enters the
light entrance surface 20a is improved.
[0050] Two-dot chain lines in the FIG. 4 indicate positions of the
light guide plate 20, the LEDs 28, and the LED board 30 when the
light guide plate 20 thermally expands. As described earlier, the
heat dissipating portion 30a of the LED board 30 is attached to the
opposite surface 20c of the light guide plate 20 and thus the LED
board 30 is fixed to the light guide plate 20. The LED board 30 is
slidable on the plate-like portion 36a of the heat dissipation
member 36. Therefore, as illustrated in FIG. 4, if the light guide
plate 20 thermally expands and the light entrance surface 20a moves
outward, the LED board 30 moves outward according to the moving of
the light entrance surface 20a. The LED board 30 moves by
substantially the same distance as the light entrance surface
moves. According to the moving of the LED board 30, the LEDs 28
that are mounted on the LED board 30 move outward by substantially
the same distance as the LED board 30 moves (i.e., by the same
distance as the light entrance surface 20a of the light guide plate
20 moves). According to this configuration, the distance between
the main light-emitting surfaces 28a of the LEDs 28 and the light
entrance surface 20a of the light guide plate 20 remains constant
before and after the thermal expansion of the light guide plate 20.
In a production process of the backlight unit 24, the LED boards 30
on which the LEDs 28 are mounted are fixed to the light guide plate
20 with the adhesive tapes 38 in advance. Therefore, during the
production process of the backlight unit 24, a shift in position of
the light guide plate 20 relative to the LED boards 30 is less
likely to occur. According to this configuration, the distance
between the main light-emitting surface 28a of the LEDs 28 and the
light entrance surface 20a of the light guide plate 20 is less
likely to change during the production process. As is described
above, in the backlight unit 24, the light entrance surface 20a of
the light guide plate 20 is less likely to come in contact with the
LEDs 28 if the thermal expansion of the light guide plate 20 occurs
or when the light guide plate 20 and the LED boards 30 are arranged
in the chassis 22 in the production step. Therefore, the LEDs 28
can be arranged relatively close to the light entrance surface 20a
and thus the light entering efficiency of light that is emitted
from the LEDs 28 into the light entrance surface 20a is
improved.
[0051] In the backlight unit 24 according to this embodiment, the
LED boards 30 are attached to the light guide plate 20 with the
adhesive tapes 38, and thus the LED boards 30 are fixed to the
light guide plate 20. With this configuration, the distance between
the LEDs 28 and the light entrance surface 20a of the light guide
plate 20 is maintained. The LED board 30 is arranged so as to be
slidable on the plate-like portion 36a. If the light entrance
surface 20a of the light guide plate 20 thermally expands toward
the LEDs 28, the LED board 30 that is fixed to the light guide
plate 20 moves according to the thermal expansion of the light
guide plate 20. Therefore, a distance between the LEDs 28 and the
light entrance surface 20a remains constant before and after the
thermal expansion. According to this configuration, a predetermined
distance is not required between the LEDs 28 and the light entrance
surface 20a for a supposed thermal expansion of the light guide
plate 20. Therefore, the LEDs 28 can be arranged close to the light
entrance surface 20a and thus the light entering efficiency of
light that is emitted from the LEDs 28 into the light entrance
surface 20a is improved. Furthermore, the heat dissipating portions
30a of the LED boards 30 are arranged on the heat dissipation
members 36 having heat dissipation properties. According to this
configuration, heat generated around the LEDs 28 is effectively
dissipated via the heat dissipation members 36. In the backlight
unit 24 of this embodiment, the heat dissipation properties are
maintained while the light entering efficiency of light that exits
the LEDs 28 and enters the light entrance surface 20a is
improved.
[0052] In the backlight unit 24 according to this embodiment, pairs
of the adhesive tapes 38, 38 are arranged between the opposite
surface 20c of the light guide plate 20 and the opposed surfaces
30a1 of the LED boards 30. Each sheet-like reflection member 40 is
arranged between the corresponding pair of the adhesive tapes 38,
38. The extending portion 40a that is one of the edge portions of
the reflection member 40 extends toward the LEDs 28 over the light
entrance surface 20a of the light guide plate 20. According to this
configuration, light that exits the LEDs 28 and travels toward the
opposed surface 30a1 is reflected by the extending portion 40a of
the reflection member 40 and directed toward the light entrance
surface 20a. Therefore, the light entering efficiency of light
emitted from the LEDs 28 into the light entrance surface 20a is
further improved.
[0053] In the backlight unit 24 according to this embodiment, the
LED boards 30 may further include the mounting portions 30b. The
mounting portion 30b has a plate-like shape and stands up from the
opposed surface 30a1 of the heat dissipating portion 30a toward the
light exit surface 20b (toward the front side). The LEDs 28 are
mounted to the mounting portion 30b. In this configuration, one of
the edge portions of the reflection member 40 extends to a position
between the LEDs 28 and the opposed surface 30a1 (i.e., immediately
below the LEDs 28). Therefore, light from the LEDs 28 is
effectively reflected toward the light entrance surface 20a by the
reflection member 40.
[0054] In the backlight unit 24 according to this embodiment, the
LED boards 30 are made of aluminum. Namely, the LED boards 30 are
components having high thermal conductivity. Therefore, heat
generated from the LEDs 28 is effectively transferred to the heat
dissipation members 36 via the LED boards 30.
Second Embodiment
[0055] A second embodiment will described with reference to the
drawings. In the second embodiment, the arrangement of LEDs 128
relative to LED boards 130 is different from the first embodiment.
Other configurations are the same as the first embodiment and thus
configurations, functions, and effects of those will not be
described. In FIGS. 6 and 7, portions indicated by numerals
including the reference numerals in FIGS. 3 and 4 with 100 added
thereto have the same configurations as the portions indicated by
the respective reference numerals in the first embodiment.
[0056] As illustrated in FIGS. 6 and 7, in a backlight unit 124
according to the second embodiment, the LED boards 130 do not
include the mounting portions 30b that are included in the LED
boards of the first embodiment. The LED boards 130 only include
heat dissipating portions 130a. The LEDs 128 are mounted on the LED
boards 130 so as to stand on an opposed surface 130a1 of each heat
dissipating portion 130a. Specifically, the LEDs 128 are arranged
on a portion of the opposed surface 130a1 so as not to correspond
to an opposite surface 120c of a light guide plate 120. The LED 128
has a surface that is mounted on the LED board 130 and the surface
is defined as a rear surface. The LED 128 further has a surface
that is one of side surfaces thereof and the one side surface faces
a light entrance surface 120a of the light guide plate 120. The
side surface of the LED 128 is a main light-emitting surface 128a.
That is, the LEDs 128 are so-called side-emitting type LEDs. If an
LED board has the mounting portion 30b and has an L-like shape in a
cross section such as the LED board of the first embodiment, a
bending work is required in advance to shape a plate member into an
LED board having an L-like cross-section during a production
process of the backlight unit 124. According to this embodiment,
the LED board 130 only includes the heat dissipating portion 130a
having a plate-like shape. Therefore, the above-described bending
work is not required for a plate member for the LED board 130
during the production process of the backlight unit 24.
Accordingly, the production cost for the LED boards 130 is reduced
and the production process for the LED boards 130 is
simplified.
Third Embodiment
[0057] A third embodiment will be described with reference to the
drawings. In the third embodiment, an attachment configuration of
opposed surfaces 230a1 of LED boards 230 to an opposite surface
220c of a light guide plate 220 is different from the first
embodiment. Other configurations are the same as the first
embodiment and thus configurations, functions, and effects of those
will not be described. In FIG. 8, portions indicated by numerals
including the reference numerals in FIG. 4 with 200 added thereto
have the same configurations as the portions indicated by the
respective reference numerals in the first embodiment.
[0058] As illustrated in FIG. 8, in a backlight unit 224 according
to the third embodiment, each of the LED boards 230 includes a step
230c that is on a portion of the opposed surface 230a1 of a heat
dissipating portion 230a. In this configuration, a part of the heat
dissipating portion 230a is located close to the opposite surface
220c of the light guide plate 220. Between the opposite surface
220c and the opposed surface 230a1, an adhesive tape 238 is
arranged. A front surface and a rear surface of the adhesive tape
238 are attached to the opposite surface 220c and the opposed
surface 230a1, respectively. Accordingly, the LED boards 230 are
fixed to the light guide plate 220. According to the configuration
in which only one adhesive tape 238 is arranged between the
opposite surface 220c and the corresponding opposed surface 230a1,
the LED board 230 is easily fixed to the light guide plate 220
during the production process of the backlight unit 224 in
comparison to the configuration of the first embodiment. If the
light entrance surface 220a of the light guide plate 220 thermally
expands toward the LEDs 228, the LED board 230 that is fixed to the
light guide plate 220 moves according to the moving of the light
entrance surface 220a. Therefore, a distance between the LEDs 228
and the light entrance surface 220a remains substantially constant
before and after the thermal expansion.
Fourth Embodiment
[0059] A fourth embodiment will be described with reference to the
drawings. In the fourth embodiment, the attachment configuration of
heat dissipation members 330 to a chassis 322 is different from the
first embodiment. Other configurations are the same as the first
embodiment and thus configurations, functions, and effects of those
will not be described. In FIG. 9, portions indicated by numerals
including the reference numerals in FIG. 4 with 300 added thereto
have the same configurations as the portions indicated by the
respective reference numerals in the first embodiment.
[0060] As illustrated in FIG. 9, in a backlight unit 324 according
to the fourth embodiment, heat dissipation members 336 constitute
part of the chassis 322. Namely, plate-like portions 336a of the
heat dissipation members 336 constitute portions of a bottom plate
322a of the chassis 322 and stand-up portions 336b of the heat
dissipation members 336 constitute peripheral walls of the chassis
322. Specifically, the plate-like portions 336a constitute end
portions of a short dimension of the bottom plate 322a (i.e., the
Y-axis direction). The stand-up portions 336b constitute long-side
peripheral walls that extend from respective long edges of the
chassis 322 toward the front side. Each of the heat dissipation
members 336 includes a heat dissipation member 336 side connecting
portion 336c at a tip of the plate-like portion 336a thereof. The
connecting portion 336c is connected to a chassis connecting
portion 322c of the bottom plate 322a of the chassis 322 with
screws. Namely, the heat dissipation members 336 are part of the
chassis 322. In the embodiment having such a configuration, the
plate-like portions 336a of the heat dissipation members 336 are
arranged so as to be in the same level with the bottom plate 322a
of the chassis 322 (i.e., positions thereof with respect to the
Z-axis direction are aligned). With this configuration, the
thickness of the backlight unit 324 is reduced in comparison to the
configuration of the first embodiment.
Fifth Embodiment
[0061] A fifth embodiment will be described with reference to the
drawings. In the fifth embodiment, the number and the arrangement
of the LED units LU are different from the first embodiment. Other
configurations are the same as the first embodiment and thus
configurations, functions, and effects of those will not be
described. In FIG. 10, portions indicated by numerals including the
reference numerals in FIG. 2 with 400 added thereto have the same
configurations as the portions indicated by the respective
reference numerals in the first embodiment.
[0062] As illustrated in FIG. 10, in a backlight unit 424 according
to the fifth embodiment, all peripheral side surfaces of a light
guide plate 420 are light entrance surfaces 420a, and the LED units
LU are arranged corresponding to all peripheral sides of the light
guide plate 420. Two of the LED units LU arranged close to
long-side peripheral surfaces of the light guide plate 420 each
have a long dimension smaller than a long-side dimension of the
light guide plate 420. In other two LED units LU arranged close to
short-side peripheral surfaces of the light guide plate 420,
plate-like portions of heat dissipation members 436 and heat
dissipating portions of LED boards 430 each have a short-side
dimension that is smaller than those in the first embodiment.
According to this configuration, although the LED units LU are
arranged corresponding to all of the peripheral sides of the light
guide plate 420, the plate-like portions of the heat dissipation
members 436 and the heat dissipating portions of the LED boards 430
in the respective LED units LU do not contact each other on an
opposite surface 420c side of the light guide plate 420. Thus, the
LED units LU can be arranged such that LEDs 428 and the light
entrance surfaces 420a are located close to one another. Adhesive
tapes are less likely to scratch or damage the light guide plate
420. Therefore, even in the configuration of the LED units LU fixed
corresponding to multiple peripheral sides of the light guide plate
420 with the adhesive tapes, functions of the light guide plate 420
are not deteriorated. In the backlight unit 424 according to this
embodiment, the LED unit LU is arranged corresponding to every
peripheral side surface of the light guide plate 420 so that
brightness of the backlight unit 424 is improved.
[0063] Modifications of the above embodiments will be listed
below.
[0064] (1) In each of the above embodiments, the heat dissipating
portions of the LED boards are in surface-contact with the
plate-like portions of the respective heat dissipation members.
However, the LED boards and the heat dissipation members may have
other configurations as long as the LED boards are arranged so as
to be slidable in the direction perpendicular to the light entrance
surface relative to the respective heat dissipation members. For
example, the heat dissipating portion may have an oval screw hole
with a major axis along the direction perpendicular to the light
entrance surface. Further, the plate-like portion of the heat
dissipation member may have a screw hole. With a screw inserted in
the both holes, the heat dissipation member may be fixed to the LED
board.
[0065] (2) In each of the above embodiments, each adhesive tape is
attached on the opposite surface such that one of the side edges of
the adhesive tape is aligned with the light entrance surface.
However, the position of the adhesive tape with respect to the
opposite surface is not limited thereto.
[0066] (3) In each of the above embodiments, the adhesive tapes
having the same dimension as the long-side dimension of the light
guide plate are attached to the opposite surface of the light guide
plate. However, the adhesive tapes may be attached to part of the
opposite surface or attached to the opposite surface at
intervals.
[0067] (4) Other than the above embodiments, the arrangement of the
adhesive tapes with respect to the opposite surface and the opposed
surfaces can be modified as appropriate.
[0068] (5) Other than the above embodiments, components arranged
between the opposite surface and the opposed surfaces can be
modified as appropriate.
[0069] (6) In each of the above embodiments, the liquid crystal
display device includes a cabinet. However, the aspect of the
present invention can be applied to the liquid crystal display
device without a cabinet.
[0070] (7) In each of the above embodiments, the liquid crystal
display device including the liquid crystal panel as the display
panel is used. However, the aspect of the present invention can be
applied to display devices including other types of display
panels.
[0071] The embodiments have been described in detail. However, the
above embodiments are only some examples and do not limit the scope
of the claimed invention. The technical scope of the claimed
invention includes various modifications of the above
embodiments.
[0072] The technical elements described in this specification and
the drawings may be used independently or in combination to achieve
the technical benefits. The combinations are not limited to those
in original claims. With the technologies described in this
specification and the drawings, multiple objects may be
accomplished at the same time. However, the technical benefits can
be achieved by accomplishing even only one of the objects.
EXPLANATION OF SYMBOLS
[0073] TV: Television device, Ca, Cb: Cabinet, T: Tuner, S: Stand,
10, 110, 210, 310, 410: liquid crystal display device, 12, 112,
212, 312, 412: bezel, 14, 114, 214, 314, 414: frame, 16, 116, 216,
316: liquid crystal panel, 18, 118, 218, 318, 418: optical member,
20, 120, 220, 320, 420: light guide plate, 20a, 120a, 220a, 320a,
420a: light entrance surface, 20b, 120b, 220b, 320b, 420b: light
exit surface, 20c, 120c, 220c, 320c, 420c: opposite surface, 22,
122, 222, 322, 422: chassis, 24, 124, 224, 324, 424: backlight
unit, 26, 126, 226, 326, 426: reflection sheet, 28, 128, 228, 328,
428: LED, 30, 130, 230, 330, 430: LED board, 36, 136, 236, 336,
436: heat dissipation member, 38, 138, 238, 338: adhesive tape, 40,
140, 340: reflection member.
* * * * *